Quick-release extruder

ABSTRACT

A bearing that provides contact force to engage a filament with a drive gear has a movable axis that can be controllably moved toward and away from the drive gear in order to engage and disengage the filament. A bearing is spring-biased toward the drive gear, and a bistable lever mechanism is provided with a first stable position in which the bearing is engaged with a filament and a second stable position in which the bearing is disengaged from the filament. By providing a mechanism that locks in both positions, loading and unloading of filament can be facilitated.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/719,874 filed on Oct. 29, 2012, the entire content of which is herebyincorporated by reference.

FIELD OF THE INVENTION

The invention generally relates to an extruder assembly, and morespecifically an extruder assembly including a quick-release extruder fora device and system for three-dimensional fabrication.

BACKGROUND

Three-dimensional printing is a process for making a three-dimensionalsolid object of virtually any shape from a digital model.Three-dimensional printing is achieved using an additive process, wheresuccessive layers of build material are laid down in different shapes.The build material may be in the form of a filament, and may include,for example, acrylonitrile butadiene styrene (ABS), high-densitypolyethylene (HDPL), polylactic acid (PLA), or any other suitableplastic, thermoplastic, or other material that can usefully be extrudedto form a three-dimensional object. The filament may be extruded usingan extruder, which may include a chamber, an opening at an extruder tip,and a motor to push the filament into the chamber and through theopening in the extruder tip.

Access to extruders is typically fairly limited. In mostthree-dimensional printing systems, a user must remove the entireextruder to perform maintenance. To remove the extruder typicallyrequires specific tools and can be a time-consuming process. Also,loading, unloading, and replacement of the filament are difficult andtime-consuming because of the lack of easy access to the components ofthe extruder assembly.

There is a need for a quick-release extruder that can allow a useraccess to the components of the extruder assembly for, e.g.,maintenance, loading, unloading, and replacement of the filament.

SUMMARY

A bearing that provides contact force to engage a filament with a drivegear has a movable axis that can be controllably moved toward and awayfrom the drive gear in order to engage and disengage the filament. Abearing is spring-biased toward the drive gear, and a bistable levermechanism is provided with a first stable position in which the bearingis engaged with a filament and a second stable position in which thebearing is disengaged from the filament. By providing a mechanism thatlocks in both positions, loading and unloading of filament can befacilitated.

In one aspect there is disclosed herein an extruder assembly including adrive gear shaped and sized to drive a filament; a bearing having afreely rotating contact surface, the bearing positioned to support thefilament against the drive gear with the freely rotating contactsurface, where an axis of the bearing is substantially parallel to anaxis of the drive gear and where the axis of the bearing is movabletoward and away from the axis of the drive gear; a spring configured tobias a position of the axis of the bearing relative to the axis of thedrive gear; and a lever positioned to apply a counterforce to the biasof the spring, thereby securing the bearing in a position to apply aconstant contact force to the filament by the bearing and the drivegear.

The extruder assembly may include an extruder as described herein, whichmay include an input opening aligned to a feedpath. The build material,which may be in the form of a filament, may travel through the openingand thus into the feedpath, which continues into a chamber of theextruder that is shaped and sized to pass the filament along thefeedpath. The filament may then travel through an orifice of theextruder, which may discharge the build material during an extrusion.

The filament may be driven by a drive gear, which may include a numberof teeth. The teeth of the drive gear may be positioned to engage thefilament before the input opening in the feedpath. Specifically, thefilament may be driven into the teeth of the drive gear with enoughforce to deform the build material, and thus the teeth of the drive gearmay grip the filament in this manner. The spring or biasing member mayprovide the force required to deform the build material into the teethof the drive gear. The drive gear may then rotate (or otherwise providemovement) such that the teeth drive the filament along the feed path,into the input opening of the extruder, through the chamber, and out ofthe orifice. It will be apparent that the drive gear may engage thebuild material in an alternate manner such that the drive gear isconfigured to drive the build material through the extruder. The drivegear may include a motor that may be integral with the drive gear orcoupled to the drive gear such that the motor rotates (or otherwisedrives) the drive gear, which may then drive the filament.

A bearing may be positioned opposite the drive gear, and it may belocated along the feedpath. The bearing may be biased by the springtoward the drive gear with a spring force such that the bearing pressesthe filament against the drive gear. The spring may be coupled to thebearing. The bearing may include a freely rotating contact surface thatis able to provide a force against the drive gear and freely rotate withthe drive gear without disengaging (when a force maintains the bearingin a position engaged with the drive gear). The spring may maintain asubstantially constant contact force of the bearing against a length ofthe filament between the bearing and the drive gear in the absence ofexternal forces. The bearing may include a smooth surface, and thebearing may be a low friction bearing. The axis of the bearing may besubstantially parallel to the axis of the drive gear.

The extruder assembly may further include a lever that may extend fromthe extruder assembly. The lever may be configured to manually move thebearing (e.g., against the biasing force of the spring) away from thedrive gear and/or away from the feedpath. Thus, the lever may be coupledto the bearing. Alternatively, the lever may be coupled to anothermechanical element (or series of elements) and then coupled to thebearing, or the lever may be coupled to the drive gear. The lever maymove the axis of the bearing away from the axis of the drive gear. Thelever may include a pivot (or several pivots), and the spring may becoupled to the lever away from the pivot. The spring may provide asubstantially constant force urging the lever into a first position or asecond position. The extruder assembly may also include a lockingmechanism to secure the lever in a position (which may be the firstposition, the second position, or another position) with the bearingmoved away from and out of the feedpath and/or drive gear. The lockingmechanism may also secure the lever in a position with the bearing movedtoward and into the feedpath and/or drive gear. The locking mechanismmay include a latch, a clamp, an electrical locking mechanism, a clip, acoupling, a dock, a hook, a pin, a snap, or the like.

The spring may include a coil spring, a compression spring, a leafspring, or the like.

The extruder assembly may further include a heating element to liquefy alength of build material in the chamber of the extruder.

An extruder assembly may include a manual control extending from theextruder assembly to manually move the bearing against the spring forceaway from the feedpath. The manual control may include a lever, a knob,a slider, a plunger, a push button, a toggle, an actuator, a screw, apiston, and the like.

The lever may also be controlled electronically, and may be activated bya user utilizing a control system, or it may be automatically activatedby a control system.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages of theinvention will be apparent from the following description of particularembodiments thereof, as illustrated in the accompanying drawings. Thedrawings are not necessarily to scale, emphasis instead being placedupon illustrating the principles of the invention.

FIG. 1 is a block diagram of a three-dimensional printer.

FIG. 2 is an exploded view of an extruder assembly.

FIG. 3 is a perspective view of an extruder assembly.

FIG. 4 is a left side view of an extruder assembly.

FIG. 5 is a front view of an extruder assembly.

FIG. 6 is a right side view of an extruder assembly.

FIG. 7 is a top view of an extruder assembly.

DETAILED DESCRIPTION

The embodiments will now be described more fully hereinafter withreference to the accompanying figures, in which preferred embodimentsare shown. This invention may, however, be embodied in many differentforms and should not be construed as limited to the illustratedembodiments set forth herein. Rather, these illustrated embodiments areprovided so that this disclosure will convey the scope of the inventionto those skilled in the art.

All documents mentioned herein are hereby incorporated in their entiretyby reference. References to items in the singular should be understoodto include items in the plural, and vice versa, unless explicitly statedotherwise or clear from the text. Grammatical conjunctions are intendedto express any and all disjunctive and conjunctive combinations ofconjoined clauses, sentences, words, and the like, unless otherwisestated or clear from the context. Thus, the term “or” should generallybe understood to mean “and/or” and so forth.

Recitation of ranges of values herein are not intended to be limiting,referring instead individually to any and all values falling within therange, unless otherwise indicated herein, and each separate value withinsuch a range is incorporated into the specification as if it wereindividually recited herein. The word “about,” when accompanying anumerical value, is to be construed as indicating a deviation as wouldbe appreciated by one of ordinary skill in the art to operatesatisfactorily for an intended purpose. Ranges of values and/or numericvalues are provided herein as examples only, and do not constitute alimitation on the scope of the described embodiments. The use of any andall examples, or exemplary language (“e.g.,” “such as,” or the like)provided herein, is intended merely to better illuminate the embodimentsand does not pose a limitation on the scope of the embodiments. Nolanguage in the specification should be construed as indicating anyunclaimed element as essential to the practice of the embodiments.

In the following description, it is understood that terms such as“first,” “second,” “above,” “below” and the like, are words ofconvenience and are not to be construed as limiting terms.

Described herein are devices, systems, and methods for using an extruderassembly including a quick-release extruder for a three-dimensionalprinter. It will be understood that while the exemplary embodimentsherein emphasize an extruder assembly for a three-dimensional printer,the principles of the invention may be adapted to other fabricationprocesses. All such variations that can be adapted to use an extruderassembly as described herein are intended to fall within the scope ofthis disclosure.

FIG. 1 is a block diagram of a three-dimensional printer. In general,the printer 100 may include a build platform 102, a conveyor 104, anextruder 106, an x-y-z positioning assembly 108, and a controller 110that cooperate to fabricate an object 112 within a working volume 114 ofthe printer 100.

The build platform 102 may include a surface 116 that is rigid andsubstantially planar. The surface 116 may support the conveyer 104 inorder to provide a fixed, dimensionally and positionally stable platformon which to build the object 112.

The build platform 102 may include a thermal element 130 that controlsthe temperature of the build platform 102 through one or more activedevices 132 such as resistive elements that convert electrical currentinto heat, Peltier effect devices that can create a heating or coolingaffect, or any other thermoelectric heating and/or cooling devices. Thusthe thermal element 130 may be a heating element that provides activeheating to the build platform 102, a cooling element that providesactive cooling to the build platform 102, or a combination of these. Theheating element 130 may be coupled in a communicating relationship withthe controller 110 in order for the controller 110 to controllablyimpart heat to or remove heat from the surface 116 of the build platform102. Thus, the thermal element 130 may include an active cooling elementpositioned within or adjacent to the build platform 102 to controllablycool the build platform 102.

It will be understood that a variety of other techniques may be employedto control a temperature of the build platform 102. For example, thebuild platform 102 may use a gas cooling or gas heating device such as avacuum chamber or the like in an interior thereof, which may be quicklypressurized to heat the build platform 102 or vacated to cool the buildplatform 102 as desired. As another example, a stream of heated orcooled gas may be applied directly to the build platform 102 before,during, and/or after a build process. Any device or combination ofdevices suitable for controlling a temperature of the build platform 102may be adapted to use as the thermal element 130 described herein.

The conveyer 104 may be formed of a sheet 118 of material that moves ina path 120 through the working volume 114. Within the working volume114, the path 120 may pass proximal to the surface 116 of the buildplatform 102—that is, resting directly on or otherwise supported by thesurface 116—in order to provide a rigid, positionally stable workingsurface for a build. It will be understood that while the path 120 isdepicted as a unidirectional arrow, the path 120 may be bidirectional,such that the conveyer 104 can move in either of two opposing directionsthrough the working volume 114. It will also be understood that the path120 may curve in any of a variety of ways, such as by looping underneathand around the build platform 102, over and/or under rollers, or arounddelivery and take up spools for the sheet 118 of material. Thus, whilethe path 120 may be generally (but not necessarily) uniform through theworking volume 114, the conveyer 104 may move in any direction suitablefor moving completed items from the working volume 114. The conveyor mayinclude a motor or other similar drive mechanism (not shown) coupled tothe controller 110 to control movement of the sheet 118 of materialalong the path 120. Various drive mechanisms are described in furtherdetail below.

In general, the sheet 118 may be formed of a flexible material such as amesh material, a polyamide, a polyethylene terephthalate (commerciallyavailable in bi-axial form as MYLAR), a polyimide film (commerciallyavailable as KAPTON), or any other suitably strong polymer or othermaterial. The sheet 118 may have a thickness of about three to aboutseven thousandths of an inch, or any other thickness that permits thesheet 118 to follow the path 120 of the conveyer 104. For example, withsufficiently strong material, the sheet 118 may have a thickness ofabout one to about three thousandths of an inch. The sheet 118 mayinstead be formed of sections of rigid material joined by flexiblelinks.

A working surface of the sheet 118 (e.g., an area on the top surface ofthe sheet 118 within the working volume 114) may be treated in a varietyof manners to assist with adhesion of build material to the surface 118and/or removal of completed objects from the surface 118. For example,the working surface may be abraded or otherwise textured (e.g., withgrooves, protrusions, and the like) to improve adhesion between theworking surface and the build material.

A variety of chemical treatments may be used on the working surface ofthe sheet 118 of material to further facilitate build processes asdescribed herein. For example, the chemical treatment may include adeposition of material that can be chemically removed from the conveyer104 by use of water, solvents, or the like. This may facilitateseparation of a completed object from the conveyer by dissolving thelayer of chemical treatment between the object 112 and the conveyor 104.The chemical treatments may include deposition of a material that easilyseparates from the conveyer such as a wax, mild adhesive, or the like.The chemical treatment may include a detachable surface such as anadhesive that is sprayed on to the conveyer 104 prior to fabrication ofthe object 112.

In one aspect, the conveyer 104 may be formed of a sheet of disposable,one-use material that is fed from a dispenser and consumed with eachsuccessive build.

In one aspect, the conveyer 104 may include a number of differentworking areas with different surface treatments adapted for differentbuild materials or processes. For example, different areas may havedifferent textures (smooth, abraded, grooved, etc.). Different areas maybe formed of different materials. Different areas may also have orreceive different chemical treatments. Thus a single conveyer 104 may beused in a variety of different build processes by selecting the variousworking areas as needed or desired.

The extruder 106 may include a chamber 122 in an interior thereof toreceive a build material. The build material may, for example, includeacrylonitrile butadiene styrene (“ABS”), high-density polyethylene(“HDPL”), polylactic acid, or any other suitable plastic, thermoplastic,or other material that can usefully be extruded to form athree-dimensional object. The extruder 106 may include an extrusion tip124 or other opening that includes an exit port with a circular, oval,slotted or other cross-sectional profile that extrudes build material ina desired cross-sectional shape.

The extruder 106 may include a heater 126 to melt thermoplastic or othermeltable build materials within the chamber 122 for extrusion through anextrusion tip 124 in liquid form. While illustrated in block form, itwill be understood that the heater 124 may include, e.g., coils ofresistive wire wrapped about the extruder 106, one or more heatingblocks with resistive elements to heat the extruder 106 with appliedcurrent, an inductive heater, or any other arrangement of heatingelements suitable for creating heat within the chamber 122 to melt thebuild material for extrusion. The extruder 106 may also or insteadinclude a motor 128 or the like to push the build material into thechamber 122 and/or through the extrusion tip 126.

In general operation (and by way of example rather than limitation), abuild material such as ABS plastic in filament form may be fed into thechamber 122 from a spool or the like by the motor 128, melted by theheater 126, and extruded from the extrusion tip 124. By controlling arate of the motor 128, the temperature of the heater 126, and/or otherprocess parameters, the build material may be extruded at a controlledvolumetric rate. It will be understood that a variety of techniques mayalso or instead be employed to deliver build material at a controlledvolumetric rate, which may depend upon the type of build material, thevolumetric rate desired, and any other factors. All such techniques thatmight be suitably adapted to delivery of build material for fabricationof a three-dimensional object are intended to fall within the scope ofthis disclosure. Other techniques may be employed for three-dimensionalprinting, including extrusion-based techniques using a build materialthat is curable and/or a build material of sufficient viscosity toretain shape after extrusion.

The x-y-z positioning assembly 108 may generally be adapted tothree-dimensionally position the extruder 106 and the extrusion tip 124within the working volume 114. Thus by controlling the volumetric rateof delivery for the build material and the x, y, z position of theextrusion tip 124, the object 112 may be fabricated in three dimensionsby depositing successive layers of material in two-dimensional patternsderived, for example, from cross-sections of a computer model or othercomputerized representation of the object 112. A variety of arrangementsand techniques are known in the art to achieve controlled linearmovement along one or more axes. The x-y-z positioning assembly 108 may,for example, include a number of stepper motors 109 to independentlycontrol a position of the extruder within the working volume along eachof an x-axis, a y-axis, and a z-axis. More generally, the x-y-zpositioning assembly 108 may include without limitation variouscombinations of stepper motors, encoded DC motors, gears, belts,pulleys, worm gears, threads, and the like. Any such arrangementsuitable for controllably positioning the extruder 106 within theworking volume 114 may be adapted to use with the printer 100 describedherein.

By way of example and not limitation, the conveyor 104 may be affixed toa bed that provides x-y positioning within the plane of the conveyor104, while the extruder 106 can be independently moved along a z-axis.As another example, the extruder 106 may be stationary while theconveyor 104 is x, y, and z positionable. As another example, theextruder 106 may be x, y, and z positionable while the conveyer 104remains fixed (relative to the working volume 114). In yet anotherexample, the conveyer 104 may, by movement of the sheet 118 of material,control movement in one axis (e.g., the y-axis), while the extruder 106moves in the z-axis as well as one axis in the plane of the sheet 118.Thus in one aspect, the conveyor 104 may be attached to and move with atleast one of an x-axis stage (that controls movement along the x-axis),a y-axis stage (that controls movement along a y-axis), and a z-axisstage (that controls movement along a z-axis) of the x-y-z positioningassembly 108. More generally, any arrangement of motors and otherhardware controllable by the controller 110 may serve as the x-y-zpositioning assembly 108 in the printer 100 described herein. Still moregenerally, while an x, y, z coordinate system serves as a convenientbasis for positioning within three dimensions, any other coordinatesystem or combination of coordinate systems may also or instead beemployed, such as a positional controller and assembly that operatesaccording to cylindrical or spherical coordinates.

The controller 110 may be electrically coupled in a communicatingrelationship with the build platform 102, the conveyer 104, the x-y-zpositioning assembly 108, and the other various components of theprinter 100. In general, the controller 110 is operable to control thecomponents of the printer 100, such as the build platform 102, theconveyer 104, the x-y-z positioning assembly 108, and any othercomponents of the printer 100 described herein to fabricate the object112 from the build material. The controller 110 may include anycombination of software and/or processing circuitry suitable forcontrolling the various components of the printer 100 described hereinincluding without limitation microprocessors, microcontrollers,application-specific integrated circuits, programmable gate arrays, andany other digital and/or analog components, as well as combinations ofthe foregoing, along with inputs and outputs for transceiving controlsignals, drive signals, power signals, sensor signals, and the like. Inone aspect, the controller 110 may include a microprocessor or otherprocessing circuitry with sufficient computational power to providerelated functions such as executing an operating system, providing agraphical user interface (e.g., to a display coupled to the controller110 or printer 100), convert three-dimensional models into toolinstructions, and operate a web server or otherwise host remote usersand/or activity through the network interface 136 described below.

A variety of additional sensors may be usefully incorporated into theprinter 100 described above. These are generically depicted as sensor134 in FIG. 1, for which the positioning and mechanical/electricalinterconnections with other elements of the printer 100 will depend uponthe type and purpose of the sensor 134 and will be readily understoodand appreciated by one of ordinary skill in the art. The sensor 134 mayinclude a temperature sensor positioned to sense a temperature of thesurface of the build platform 102. This may, for example, include athermistor or the like embedded within or attached below the surface ofthe build platform 102. This may also or instead include an infrareddetector or the like directed at the surface 116 of the build platform102 or the sheet 118 of material of the conveyer 104. Other sensors thatmay be usefully incorporated into the printer 100 as the sensor 134include a heat sensor, a volume flow rate sensor, a weight sensor, asound sensor, and a light sensor. Certain more specific examples areprovided below by way of example and not of limitation.

The sensor 134 may include a sensor to detect a presence (or absence) ofthe object 112 at a predetermined location on the conveyer 104. This mayinclude an optical detector arranged in a beam-breaking configuration tosense the presence of the object 112 at a location such as an end of theconveyer 104. This may also or instead include an imaging device andimage processing circuitry to capture an image of the working volume 114and analyze the image to evaluate a position of the object 112. Thissensor 134 may be used for example to ensure that the object 112 isremoved from the conveyor 104 prior to beginning a new build at thatlocation on the working surface such as the surface 116 of the buildplatform 102. Thus the sensor 134 may be used to determine whether anobject is present that should not be, or to detect when an object isabsent. The feedback from this sensor 134 may be used by the controller110 to issue processing interrupts or otherwise control operation of theprinter 100.

The sensor 134 may include a sensor that detects a position of theconveyer 104 along the path. This information may be obtained from anencoder in a motor that drives the conveyer 104, or using any othersuitable technique such as a visual sensor and corresponding fiducials(e.g., visible patterns, holes, or areas with opaque, specular,transparent, or otherwise detectable marking) on the sheet 118.

The sensor 134 may include a heater (instead of or in addition to thethermal element 130) to heat the working volume 114 such as a radiantheater or forced hot air to maintain the object 112 at a fixed, elevatedtemperature throughout a build. The sensor 134 may also or insteadinclude a cooling element to maintain the object 112 at a predeterminedsub-ambient temperature throughout a build.

The sensor 134 may also or instead include at least one video camera.The video camera may generally capture images of the working volume 114,the object 112, or any other hardware associated with the printer 100.The video camera may provide a remote video feed through the networkinterface 136, which feed may be available to remote users through auser interface maintained by, e.g., remote hardware, or within a webpage provided by a web server hosted by the three-dimensional printer100. Thus, in one aspect there is a user interface adapted to present avideo feed from at least one video camera of a three-dimensional printerto a remote user through a user interface.

The sensor 134 may include may also include more complex sensing andprocessing systems or subsystems, such as a three-dimensional scannerusing optical techniques (e.g., stereoscopic imaging, or shape frommotion imaging), structured light techniques, or any other suitablesensing and processing hardware that might extract three-dimensionalinformation from the working volume 114. In another aspect, the sensor134 may include a machine vision system that captures images andanalyzes image content to obtain information about the status of a job,working volume 114, or an object 112 therein. The machine vision systemmay support a variety of imaging-based automatic inspection, processcontrol, and/or robotic guidance functions for the three-dimensionalprinter 100 including without limitation pass/fail decisions, errordetection (and corresponding audible or visual alerts), shape detection,position detection, orientation detection, collision avoidance, and thelike.

Other components, generically depicted as other hardware 135, may alsobe included, such as input devices including a keyboard, touchpad,mouse, switches, dials, buttons, motion sensors, and the like, as wellas output devices such as a display, a speaker or other audiotransducer, light emitting diodes, and the like. Other hardware 135 mayalso or instead include a variety of cable connections and/or hardwareadapters for connecting to, e.g., external computers, external hardware,external instrumentation or data acquisition systems, and the like.

The printer 100 may include, or be connected in a communicatingrelationship with, a network interface 136. The network interface 136may include any combination of hardware and software suitable forcoupling the controller 110 and other components of the printer 100 to aremote computer in a communicating relationship through a data network.By way of example and not limitation, this may include electronics for awired or wireless Ethernet connection operating according to the IEEE802.11 standard (or any variation thereof), or any other short or longrange wireless networking components or the like. This may includehardware for short range data communications such as BlueTooth or aninfrared transceiver, which may be used to couple into a local areanetwork or the like that is in turn coupled to a data network such asthe Internet. This may also or instead include hardware/software for aWiMax connection or a cellular network connection (using, e.g., CDMA,GSM, LTE, or any other suitable protocol or combination of protocols).Consistently, the controller 110 may be configured to controlparticipation by the printer 100 in any network to which the networkinterface 136 is connected, such as by autonomously connecting to thenetwork to retrieve printable content, or responding to a remote requestfor status or availability.

An extruder assembly including a quick-release extruder will now bedescribed.

The extruder assembly with a quick-release extruder may include any ofthe features described herein including the features described in U.S.Provisional Application No. 61/719,874, which is hereby incorporated byreference in its entirety.

In a three-dimensional printer, a filament of build material may besupported by and in contact with a drive gear. Also, a filament of buildmaterial may be in contact with a drive gear via a bearing, which may bea spring-loaded bearing or the like. The bearing may provide asubstantially constant contact force against the filament and toward thedrive gear. The bearing may include a quick-release lever or the like tomove the bearing away from the drive gear for, e.g., access to andmaintenance of an extruder assembly. This arrangement may also permitquick loading, unloading, and replacement of filament of material for athree-dimensional printer.

FIG. 2 is an exploded view of an extruder assembly 200. In general, theextruder assembly 200 may include a drive gear 202 with an arrangementof teeth 210 or other protrusions to grip and advance a filament (notshown) through the extruder assembly 200. The drive gear 202 may bedisposed adjacent to a feedpath passing through the extruder assembly200 along which a filament of build material travels during anextrusion. The feedpath may be defined by the path taken by the filamentthrough the extruder assembly 200, where the filament enters thefeedpath through an input opening 212, travels through a chamber 214,engages with a drive gear 202 and a bearing 204, and travels through anopening 216 in a heating block 218. Alternatively, the feedpath may bedefined as the path taken by the filament before and after engagementwith the drive gear 202. The opening 216 for the feedback may be formedin the heating block 218, which may include a heating element,thermistors, and so forth for heating the heating block and creating amelt chamber within the opening 216. An extrusion tip may be formed intoa bottom of the opening 216, or the bottom of the opening 216 may bethreaded to removably and replaceably receive a nozzle having on orificeto extrude liquefied material with a desired cross sectional shape. Thedrive gear 202 may be powered by any suitable electromechanical devicesuch as a stepper motor or the like, and imparts a drive force on afilament by gripping the filament with the teeth 210 and rotating tomove the filament along the feedpath.

A bearing 204 may be any free-rolling contact surface that can applyforce normal to the drive gear 202 in order for the teeth 210 toengagement the filament without inhibiting motion of the filament alongthe feedpath. The bearing 204 may have a smooth, substantiallycylindrical exterior, and may be positioned on an axis 220 substantiallyparallel to an axis 222 of the drive gear 202. The bearing 204 may alsohave a different shape than is shown in FIG. 2, which may be based onthe configuration and/or type of the drive gear and/or build materialand/or filament used with the extruder assembly 200. Additionally, thebearing 204 may generally include any suitable mechanical components forrelatively low-friction rotation about its axis. A variety of rollingand hydrostatic bearings and the like are known in the art, any of whichmay be used as the bearing 204 described herein.

The bearing 204 may be disposed such that it is at a distance where itmay apply a force against the drive gear 202 to a filament of suitablediameter that passes between the drive gear 202 and the bearing 204. Aspring 206 may be positioned to apply a substantially constant force tothe bearing 204 toward the drive gear 202 so that the drive gear 202 canengage the filament. This arrangement advantageously permits the drivegear 202 and bearing 204 to accommodate defects in a filament andvariations in filament diameter while maintaining a consistent grippingforce to drive the filament. A coil spring may conveniently be employedas the spring 206, however a variety of springs and biasing members areknown in the art that may be adapted to provide a biasing force tomaintain a position of the bearing 204 and/or the drive gear 202relative to one another. Moreover, the force to maintain a position ofthe bearing and/or the drive gear relative to one another may beprovided by an actuator, a piston, or the like.

A lever 208 may be provided as a mechanism to position the bearing 204relative to the drive gear 202. By operating the lever 208, the bearing204 may be moved closer to the drive gear 202 (e.g., in order to engagea filament) or farther from the drive gear 202 (e.g., in order todisengage the filament for removal or other maintenance). It will beunderstood that the lever may be simple lever, e.g., a spring-loadedlever on a pivot. In an embodiment, when the lever is in a firstposition the bearing is engaged with the drive gear, and when the leveris in a second position the bearing is disengaged from the drive gear.It will also be understood that the lever 208 may be a bistable lever orthe like, where the bistable lever may be associated with a second lever224 (as shown in FIG. 2) that is directly coupled to an axle 225 of thebearing 204. In this configuration, the second lever 224 is urged by thespring 206 toward the drive gear 202 about a pivot 227 in the absence ofexternal forces. The lever 208 can then be operated to contact a beveledsurface 229 of the second lever 224 and drive the second lever 224 awayfrom the drive gear 202 against the force of the spring 206. An arm ofthe lever 208 may extend from the extruder assembly 200 for handmanipulation. Bistable operation of the lever 208 may be achieved, forexample, by forming an L near the pivot point (as illustrated below inFIG. 6) that locks the bearing 204 in an open (i.e., away from the drivegear) position when the lever 208 is moved beyond a certain rotation. Inthis respect, the L cooperates with the beveled surface 229 to create aforce that retains the open position when the lever 208 is moved to oneside. Thus the assembly has a first stable position (a “closed position)in which the bearing engages a filament with the drive gear and a secondstable position (an “open position”) in which the bearing does notengage a filament with the drive gear.

An example of a lever is shown in FIG. 2, but it will be understood thatdifferent types of levers and/or mechanical elements may be used tosimilar affect. For example, the lever may further include additionallevers, pivoting links, and the like that cooperate to move the bearingfrom a first position where it is engaged with the drive gear to asecond position where it is disengaged from the drive gear. Similarly,while the bistable lever described above automatically locks in an openor closed position, manual locking mechanism may also or instead beemployed, such as with a single spring-loaded lever and an externallocking mechanism that can secure the bearing 204 in an open positionagainst the force of a spring.

Further, it will be understood that a variety of mechanical arrangementsmay be used to similar affect to release the extruder assemblycomponents. The lever may also or instead include a button, a knob, aslider, or any other mechanical arrangement suitable for moving thebearing 204 into and out of engagement with the drive gear 202, or moregenerally farther from or closer to the drive gear 202, which mayinclude moving the axle 225 of the bearing 204 farther from or closer tothe drive gear 202, preferably while maintaining a generally parallelorientation of the axis 222 of the drive gear with the axis 220 of thebearing. It will be appreciated that the two axes 220, 222 need not beperfectly parallel at all times and that, by way of example, the axes220, 222 may move out of a parallel arrangement when the axis 220 of thebearing is moved away from the axis 222 of the drive gear for loadingand unloading of a filament. All such arrangements suitable for tensioncontrol and/or quick release may be used with the extruder assembliesdescribed herein, and are intended to fall within the scope of thisdisclosure.

FIGS. 3-7 show a number of views of an extruder assembly that may beused as any of the extruder assemblies described above.

FIG. 3 shows a perspective view of an extruder assembly 300, where thefeedpath 301, drive gear 302, bearing 304, lever 308, and input opening312 are visible. Also, as shown in FIG. 3, the extruder assembly 300 maygenerally include a housing 303 for the components of the extruderassembly 300, which may be a two-part housing formed of two portionsthat can be joined for use as an extruder assembly. While the housingmay also be formed as a single integral piece, a two-part constructionadvantageously facilitates disassembly to service parts within theextruder assembly 300.

FIG. 4 shows a left side view of an extruder assembly 400, where thefeedpath 401, drive gear 402, bearing 404, lever 408, and input opening412 are visible. Also, as shown in FIG. 4, the extruder assembly 400 maygenerally include a housing 403 for the components of the extruderassembly 400.

FIG. 5 shows a front view of an extruder assembly 500, where thefeedpath 501, lever 508, and input opening 512 are visible. Also, asshown in FIG. 5, the extruder assembly 500 may generally include ahousing 503 for the components of the extruder assembly 500.

FIG. 6 shows a right side view of an extruder assembly 600, where thefeedpath 601, drive gear 602, bearing 604, spring 606, lever 608, inputopening 612, and second lever 624 are visible. As shown in FIG. 6, thelever 608 may be disposed in a first position (as shown in FIG. 6, i.e.,where the lever 608 rests on the right side of the extruder assembly600), where the bearing 604 is engaged with the drive gear 602. If thelever 608 is manually moved from the right side of the extruder assembly600 to the left side of the extruder assembly 600, the second lever 624can rotate about a pivot (not shown) against a biasing force of thespring 606 so that the bearing 604 moves out of engagement with thedrive wheel 602. Although not illustrated, it will be noted that an L630 on the lever 608 can be shaped so that in this second position, anupward force between the L 630 and the beveled end of the second lever624 retains the lever 608 and the second lever 624 in the open positionto provide a bistable lever. In another aspect, the L may be omitted andthe bearing 604 may be urged into engagement with the drive gear 602whenever an external force is removed from the lever 608.

FIG. 7 shows a top view of an extruder assembly 700, where the lever 708and input opening 712 are visible. Also, as shown in FIG. 7, theextruder assembly 700 may generally include a housing 703 for thecomponents of the extruder assembly 700.

While particular embodiments have been shown and described, it will beapparent to those skilled in the art that various changes andmodifications in form and details may be made therein without departingfrom the spirit and scope of this disclosure and are intended to form apart of the invention as defined by the following claims, which are tobe interpreted in the broadest sense allowable by law.

What is claimed is:
 1. An extruder assembly comprising: an extrudercomprising an input opening aligned to a feedpath for a filament ofbuild material, a chamber shaped and sized to pass the build materialalong the feedpath, and an orifice to discharge the build material in anextrusion; a drive gear having a number of teeth positioned to engagethe filament in the feedpath; a bearing positioned opposite the drivegear along the feedpath; a spring coupled to the bearing and biasing thebearing toward the drive gear with a spring force; a lever extendingfrom the extruder assembly to manually move the bearing against thespring force away from the feedpath; and a locking mechanism to securethe lever in a position with the bearing moved away from and out of thefeedpath.
 2. The extruder assembly of claim 1 further comprising a motorcoupled to the drive gear and operable to rotate the drive gear.
 3. Theextruder assembly of claim 1 wherein the bearing comprises a freelyrotating contact surface.
 4. The extruder assembly of claim 1 wherein anaxis of the bearing is substantially parallel to an axis of the drivegear.
 5. The extruder assembly of claim 4 wherein the lever moves theaxis of the bearing away from the axis of the drive gear.
 6. Theextruder assembly of claim 1 further comprising a pivot for the lever,wherein the spring is coupled to the lever away from the pivot.
 7. Theextruder assembly of claim 1 wherein the locking mechanism includes abistable lever including a mechanical linkage to the bearing, thebearing engaged with the drive gear when the bistable lever is in afirst position and the bearing disengaged from the drive gear when thebistable lever is in a second position.
 8. The extruder assembly ofclaim 1 wherein the spring is a coil spring.
 9. The extruder assembly ofclaim 1 wherein the spring force provides sufficient force to engage thebuild material with the drive gear.
 10. The extruder of claim 1 whereinthe spring force provides sufficient force to deform the build materialinto the number of teeth of the drive gear.
 11. The extruder assembly ofclaim 10 wherein the build material includes a filament of one or moreof acrylonitrile butadiene styrene (ABS), high-density polyethylene(HDPL), and polylactic acid (PLA).
 12. The extruder assembly of claim 1wherein the spring maintains a substantially constant contact force ofthe bearing against a length of filament between the bearing and thedrive gear in an absence of external forces.
 13. The extruder assemblyof claim 1 wherein the bearing is a low friction bearing.
 14. Anextruder assembly comprising: an extruder comprising an input openingaligned to a feedpath for a filament of build material, a chamber shapedand sized to pass the build material along the feedpath, and an orificeto discharge the build material in an extrusion; a drive gear having anumber of teeth positioned to engage the filament before the inputopening in the feedpath; a bearing positioned opposite the drive gearalong the feedpath; a spring element coupled to the bearing and biasingthe bearing toward the drive gear with a spring force; a manual controlextending from the extruder assembly to manually move the bearingagainst the spring force away from the feedpath; and a locking mechanismto secure the manual control in a position with the bearing moved awayfrom and out of the feedpath.
 15. The extruder assembly of claim 14wherein the manual control includes a lever.
 16. The extruder assemblyof claim 14 wherein the manual control includes one or more of a knob, aslider, a plunger, and a push button.
 17. The extruder assembly of claim14 wherein the spring element includes a coil spring.
 18. The extruderassembly of claim 14 wherein the spring element includes a compressionspring.
 19. The extruder assembly of claim 14 further comprising aheating element to liquefy a length of build material in the chamber ofthe extruder.
 20. The extruder assembly of claim 14 wherein the lockingmechanism includes a bistable lever including a mechanical linkage tothe bearing, the bearing engaged with the drive gear when the bistablelever is in a first position and the bearing disengaged from the drivegear when the bistable lever is in a second position.